The Food and Drug Administration on Thursday approved unrestricted sales of Plan B One-Step, lifting all age limits on the emergency contraceptive.

The move came a week after the Obama administration ended months of back-and-forth legal battles by promising a federal judge it would take that step. Women's health advocates had pushed for easier access to next-day birth control for more than a decade.

"Over-the-counter access to emergency contraceptive products has the potential to further decrease the rate of unintended pregnancies in the United States," FDA drug chief Dr. Janet Woodcock said in a statement announcing the approval.

It wasn't clear how quickly Plan B One-Step would move from behind pharmacy counters to sit on drugstore shelves. Until now, customers could buy that morning-after pill and competing generic versions without a prescription only if they proved to a pharmacist that they were 17 or older. FDA said the product will have to be repackaged to reflect the change; maker Teva Women's Health didn't immediately respond. FDA has not lifted age limits on competing generics.

The morning-after pill contains a higher dose of the hormone in regular birth control pills. Taking it within 72 hours of rape, condom failure or just forgetting regular contraception can cut the chances of pregnancy by up to 89 percent, but it works best within the first 24 hours. If a girl or woman already is pregnant, the pill, which prevents ovulation or fertilization of an egg, has no effect.

Back in 2011, the FDA was preparing to allow over-the-counter sales of emergency contraceptives with no limits when Health and Human Services Secretary Kathleen Sebelius overruled her own scientists in an unprecedented move. She said she worried that girls as young as 11 could use the pill with no supervision, a concern that President Barack Obama echoed.

In April, U.S. District Judge Edward Korman blasted that decision as putting politics ahead of science and ordered the FDA to allow unrestricted sales of emergency contraceptives. He said hardly any 11-year-olds would use the pill, which costs about $50. The Obama administration lost a round in the appeals court, too, before telling the judge it would approve the one-pill brand.

Doctors' groups and contraceptive advocates have long argued that easier access to emergency contraceptives would cut unintended pregnancies and said the drugs are safe even when used at young ages.

Social conservatives, in contrast, complain that lifting prescription requirements undermines the rights of parents and could endanger girls.